The subject invention relates to systems and methods for controlling a motor and, more particularly, to systems and methods for controlling operation of a torque-assist motor of an electrical power-assist system of a motor vehicle.
In a permanent magnet machine, in which current is controlled using a feedback controller, such as a PI controller, either or both of the proportional gain and the integral gain can be adjusted to achieve increased frequency response, and thus greater bandwidth. Unfortunately, however, increases in gain often entail the negative consequence of amplifying noise that is inherent in the feedback signal (e.g., the current signal). In a vehicle steering system with electric power assist, the amplification of noise associated with the current that drives the assist motor can produce vibrations in the vehicle steering handwheel, which vibrations may be particularly noticeable when the vehicle is stationary or moving at a relatively low speed such that an operator might expect to experience little to no handwheel vibration.
Accordingly, it is desirable to have an improved system and method for controlling electric power assist of vehicle steering systems wherein current gain may be adjusted so as to achieve increased frequency response (i.e., bandwidth) while also providing for attenuation of handwheel vibration at relatively low speeds.